The goal of this project is to understand how (B-Ras1 and (B-Ras2, members of an unusual sub-class of Ras-like proteins, are regulated, and how they in turn regulate pathways leading to NF-(B and Ral GTPases. These proteins were originally discovered through their physical interaction with the I(B( protein, and in vitro and overexpression experiments indicated that they are inhibitors of NF-(B. However the true physiological role of these proteins has remained unclear. Our preliminary results using knock-outs of both (B-ras genes shows that they act to inhibit both NF-(B and Ral GTPase pathways. Interestingly, mice lacking (B-Ras proteins also die perinatally due to defects in lung development. In this research proposal we aim to ask the following questions. In Aim 1 we will study how (B-Ras actually regulates NF-(B. While affecting the stability of I(B( is a likely mechanism, many questions about exactly how (B-Ras functions remains unanswered. Availability of cells lacking (B-Ras will allow us to explore the underlying mechanism in a systematic manner. We will also use mice lacking (B-Ras in macrophages to study mouse models of inflammation including septic shock and collagen-induced arthritis. In Aim 2 we will ask how (B-Ras regulates Ral, and determine whether activated Ral contributes to NF-(B activation. We will study the mechanism by which growth factor signaling disrupts the (B-Ras-RalGAP complex, and determine why binding to (B-Ras inhibits the activity of RalGAP. We will also test whether the activated Ral in (B-Ras deficient cells contributes to NF-(B activation. Finally in Aim 3 we will explore the lung phenotype seen in the (B-Ras-deficient animals. We will study the mechanism of dysregulated surfactant expression, in particular the role of NF-(B in the process. In summary these studies will provide significant new insight into the biology of these evolutionarily conserved, yet enigmatic, members of this Ras-like family of proteins.